Vehicles such as hybrid cars or electric cars drive a driving motor or a motor of a compressor by using a high voltage battery and drive an audio device or a communication device such as a local interconnect network (LIN) or a controller area network (CAN) by using a low voltage battery. In such a construction, for example, in a case where a motor control unit that controls an operation of an inverter apparatus and a communication control unit that controls an operation of the communication device transmit and receive signals between each other, a photo coupler is used to transmit and receive signals.
In general, an apparatus for controlling an inverter 40 and driving a motor 60, as shown in FIG. 1, includes a high voltage battery 10, a voltage converter 20 that converts a voltage of the high voltage battery 10 into another voltage, a smoothing unit (a filter condenser) 30 that stores and smoothes out the converted voltage, the inverter (a D/C converter) 40 that converts a direct current voltage of the smoothing unit 30 into an alternating current voltage, the motor 60 driven by the alternating current voltage of the inverter 40, and a control unit 50 that controls an output frequency.
The inverter 40 uses switching elements which are connected. In general, a semiconductor element that is an insulated gate bipolar transistor (IGBT) having an excellent characteristic as a switching element is mainly used.
If an output short or an arm short occurs in the inverter 40 and a short current flows through the IGBT that is the switching element, the short current of the switching element increases to a maximum current allowed by a gate-emitter voltage (VGE) applied to the switching element, and a collector-emitter voltage (VCE) of the switching element increases in proportional to the current. In a case where an uncontrolled current (hereinafter referred to as an “accident current”) flows in the IGBT that is the switching element of the inverter 40 due to the short current as described above, an appropriate measure needs to be taken by detecting the accident current.
To this end, conventionally, a separate detection dedicated circuit that controls current and detects a short current by using current values detected by phase output current detection sensors 70 (70a, 70b, and 70c) installed at a phase output for current control needs to be provided.
For example, in a normal case, if the switching element is turned on, an input voltage VCC is connected to ground GND through a pull-up resistance, a current limitation resistance, a blocking diode, and the switching element. In this regard, a turn-on voltage of the switching element is only detected to perform a normal operation. To the contrary, in a case where the switching element is turned off, the turn-on voltage of the switching element increases in proportional to a size of the short current and is compared to a reference voltage of a comparison unit to determine whether the short current is detected, and a failure signal is transmitted to the control unit 50.
However, the apparatus for controlling the inverter 40 including the detection dedicated circuit having a function of detecting the short current according to the conventional art needs a separate current detection sensor, which problematically causes an increase in cost. Further, the apparatus for controlling the inverter 40 separately performs current detection sensing, which problematically increases a load of a control unit. Furthermore, the conventional current detection sensor is problematically incapable of adjusting a short current detection level.